How we treat your water

We work around the clock to supply top quality drinking water to 2.1 million customers in Kent, Sussex, Surrey, Hampshire and Berkshire.

Every day we supply 565 million litres of drinking water from our water treatment works, piped through more than 14,500 kilometres of water mains to our customers' taps.

Three-quarters of the water is pumped from underground aquifers - this water is relatively easy to treat because it has already been naturally filtered through chalk or sandstone. It only needs to be disinfected with chlorine to make it safe to drink.

However, water taken from rivers and surface reservoirs requires more treatment stages to ensure it meets the exacting standards set by the Drinking Water Inspectorate.

How we treat your water:

Below is a brief description of the main types of water treatment we use:


As water is stored in reservoirs, debris and solids settle to the bottom and sunlight breaks down organic material.


Water passes through fine screens, removing larger material such as sticks and weeds.

Primary Treatment

Ozone is bubbled through the water and a form of iron is added. This process forms small particles, called 'floc', which attract impurities.


The floc is stirred to increase the size of the particles, which sink to the bottom and are removed.


Filtration sieves the water, and using slow sand filters also encourages bacteria to grow, breaking down organic compounds in the water.


This process removes compounds such as hydrogen sulphide and carbon dioxide, and oxidises dissolved metals.

Advanced Treatment

Water is treated with granular activated carbon (GAC), while ozone gas is bubbled through it. This disinfects the water, and removes pesticides.


Chlorine disinfects all water supplies, to eliminate potentially harmful micro-organisms such as bacteria.

Sludge Treatment

Finally, waste products produced during the treatment processes are themselves treated, with clean water returned to the environment and solid matter recycled into fertiliser.

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Making it crystal clear: read our water quality leaflet

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